With the availability of new and improved materials, golf clubs are continuously being made stronger and lighter to provide maximum flying distance to the ball. One of the difficulties in designing a golf club is the "trampoline effect" of the golf club head, which increases the launch velocity of a ball. The club head typically has a face plate that deforms when the face plate strikes the ball. Behaving like a spring, the face plate rebounds to give the ball a higher launch velocity. This is known as the trampoline effect. Higher face plate deformation may be realized by using a thin face plate with materials that have low stiffness (Young's modulus) and high strength. Materials that have these properties include titanium, a new alloy and glass or graphite reinforced composite materials.
Recently the U.S. Golf Association (USGA) has determined that the trampoline effect does occur. In order to preserve the game as a game of skill, the USGA has resolved not to permit technology to overwhelm the game. In October 1998, the USGA has adopted a regulation that limits excessive launch velocity of a golf ball. In essence, the rule stipulates that any club head, which impacts a golf ball at a velocity of 160 ft/sec will be considered nonconforming, if it has a coefficient of restitution greater than 0.83.
A typical golf club head using new materials is disclosed in U.S. Pat. No. 5,064,197. The disclosure describes a method to adjust the sound characteristics of a metal "wood" club head upon impacting a golf ball. The club head includes a pair of chambers filled with air, liquid or solid. The forward chamber is covered with a plate formed of metal that is designed to maximize the flying distance of the ball. The disclosure suggests that if the face plate is made thinner, a trampoline-like effect may be produced that may enhance the propulsion effects of the club head against the struck ball. There is no further disclosure in this patent, however, why such propulsion effects occur or how these effects may be tuned to the individual golfer.
U.S. Pat. No. 5,807,190 discusses use of various materials in golf club heads to achieve greater distance and more control over a ball. Since mechanical characteristics of the club face determines the trajectory and distance of the ball, the Patent discloses that controlling the characteristics of the face plate is the key to controlling speed and distance of the ball. The striking face of the golf club includes different zones of material. One or more of the zones may be of material having a first predetermined modulus of elasticity, and one or more of the other zones may be of material having a second predetermined modulus of elasticity. These zones may be made from a unitary piece of material or from different materials, such as titanium and stainless steel. These materials may be applied to the club face monolithically or as inserts, and include polymers, ceramics and metals. The most common materials are stainless steel, BeCu, titanium alloys and shape memory materials, such as NiTi and copper based alloys. U.S. Pat. No. 5,807,190 is incorporated herein by reference for its teachings of applying various materials to the face of a club to control speed and distance of a ball.
Another patent incorporated herein by reference for its teachings of adjusting a club face to the skill level of the golfer is U.S. Pat. No. 5,505,453. This reference is directed to a strike plate of desired thickness having a bulbous portion formed on a rear face of the strike plate. A removable tennis racket-like head with a plurality of tension strings is mounted behind the strike plate. The tension strings may be fabricated from high strength materials such as carbon, fiberglass, stainless steel, etc. In this manner, the golf club head may be "tuned" to the individual skill levels of the players. By selecting different materials and structures for the face plate of the golf club head, the launch velocity of the ball may be controlled.